The present invention relates to compounds and copolymers based on and formed from substituted imidazoles, particularly from vinyl dicyanoimidazoles and methods of preparing such copolymers. More particularly, the present invention pertains to copolymers which incorporate 4,5-dicyano-2-vinylimidazole and its derivatives.
Vinyl dicyanoimidazoles are a family of substituted imidazole compounds which can be made from the oxidation of reaction products synthesized by carefully controlled Schiff base reactions of diaminomaleonitrile (DAMN) with several conjugated aldehydes. Vinyl dicyanoimidazoles and their derivatives can polymerize to form homopolymers which exhibit desirable characteristics such as elevated glass transition temperature and flammability resistance. Incorporation of vinyl dicyanoimidazoles and derivatives thereof into copolymerized materials with various existing monomeric compounds would be desirable but, heretofore has not been accomplished.
To date, various copolymer-forming methodologies exist. Formulation of copolymers from unsubstituted imidazoles is discussed in the work of K. L. Petrak, Journal of Polymer Science: Polymer Letters Edition, 16, 393-399 (1978). However, unsubstituted imidazoles behave very differently from 4,5 dicyano substituted imidazoles. For example, proton acidities differ by nine orders of magnitude due to significant differences in polarity and available resonance structures.
Predictions regarding which monomers will react together successfully to form copolymers is difficult to do with consistency and accuracy. Prediction has been attempted by several methods. The best known method, often called the Q-e scheme is due to Alfrey and Price and is described in standard reference texts such as Odian, Principles of Polymerization, 3rdEdition, Wiley-Interscience 1991, at pages 489-91. In the Q-e scheme, an attempt is made to correlate the resonance (Q) and polarity factors (e) of the monomers with their behavior in copolymerization. Empirically, it has been found that monomers of very different Q""s copolymerize poorly. However, the precision or accuracy of the available Q and e values is often poor. Thus, correlation is generally successful in hindsight, but has proven to be of limited predictive value. Thus successful copolymerization of various monomers with substituted imidazoles would not be easily predicted from the technology as it existed heretofore.
Presently there is a need for copolymers which retain many of the advantageous characteristics of homopolymeric compositions but exhibit enhanced thermal stability and flame retardance, for example. In spite of a great many efforts and much desire, it is difficult to bring new monomers and polymers into the high volume market due, in part, to high capital costs and stringent controls over feedstocks and processing. Thus, the ability to identify and incorporate various loadings of a monomer or comonomer into a copolymeric matrix to effect performance improvement at low cost is highly desired. It is also desirable that the resulting copolymer be thermally robust, and be capable of forming stable coatings.
It is an object of the present invention to provide novel copolymers which incorporate substituted imidazoles, particularly cyano-substituted imidazoles into the respective copolymeric matrix. The substituted imidazole contemplated in the present invention may be incorporated as either a monomer or homopolymer. It is also contemplated that the substituted imidazole which may be incorporated is a copolymeric material.
More particularly, it is an object of the present invention that the compound which may be incorporated is a 4,5-dicyano-2-vinylimidazole (also referred to hereafter as xe2x80x9cVINAZENE(trademark)xe2x80x9d) or derivatives thereof; present initially as a monomer or homopolymer. It is also contemplated that the VINAZENE(trademark) or VINAZENE(trademark) derivative which is incorporated may be present initially as a copolymer with other compounds deemed useful to the make-up of the final copolymeric compound.
It is a further object of the present invention that the VINAZENE(trademark) or VINAZENE(trademark) derivatives be polymerizable with various standard monomers to form novel copolymers, terpolymers and the like. The various 4,5-dicyano-2-vinylimidazoles which can be employed in the present invention are, preferably, those having the formula as per FIG. 1 in which R1 is characterized as being hydrogen or an organic substitute which does not interfere with polymerization and/or copolymerization and is attachable to the cycle compound by an electrophilic agent.
It is also an object of this invention to provide processes and methods whereby VINAZENE(trademark) and VINAZENE(trademark)-derivatives can copolymerized to form novel and enhanced polymeric material. Further objects of the present invention will become apparent in reading the specification of the present invention.
Generally speaking, the present invention is directed to new polymeric materials in which substituted imidazoles, namely vinyl dicyanoimidazoles, are incorporated into a copolymeric or terpolymeric matrix with various known monomers. Specifically, the copolymer or terpolymeric matrix contemplated in the present invention will contain 4,5-dicyano-2-vinylimidazole (VINAZENE(trademark)) or derivatives thereof, with 1-alkyl derivatives having 1 to 12 carbon atoms being particularly favored. The other monomers employed in the copolymeric matrix may be any monomeric compound which typically is capable of undergoing copolymerization reactions, with monomers capable of undergoing addition polymerization being particularly favored. Such monomers include, but are not limited to conjugated dienes such as styrene, styrene derivatives, isoprene, butadiene, chloroprene and, cyclopentadiene, substituted acrylate esters, alkyl acrylate esters and methacrylates, with methyl methacrylate being particularly preferred. Other materials which can be employed as monomers include materials such as acrylonitrile or other vinylic monomers. It is to be understood that the foregoing list is deemed to be illustrative of suitable monomers rather than imitative of the present invention.